The world's first photograph was taken in 1826 using a pinhole camera, known as camera obscura. The camera obscura, the basic projection model of pinhole cameras, was already known in China more than 2500 years ago. Cameras used since this first photograph are basically following the pinhole camera principle. The quality of projected images improved due to progress in optical lenses and silver-based film, the latter one replaced today by digital technologies. Pinhole-type cameras are still the dominating brands and are also used in computer vision for understanding 3D scenes based on captured images or videos. However, different applications have pushed for designing alternative architectures of cameras. For example, in photogrammetry, cameras are installed in planes or satellites, and a continuing stream of image data can also be created by capturing images just line by line, one line at a time. As a second example, robots are required to understand scenery in full 360 degrees to be able to react to obstacles or events; a camera looking upward into a parabolic or hyperbolic mirror allows this type of omnidirectional viewing. The development of alternative camera architectures results in a need to understand related projective geometries for the purpose of camera calibration, binocular stereo, static or dynamic scene understanding. Written by leading researchers in the field, this book elucidates on these topics as well as some of the applications of alternative camera architectures.